Ecological Enhancement Works in River Channels Smart, Green and - PowerPoint PPT Presentation

Ecological Enhancement Works in River Channels Smart, Green and Resilient Stormwater Management Ms. Julia W. Y. CHAN 14 November 2017 Drainage Services Department – Research & Development Forum 2017

Agenda 1. Background of the Eco-hydraulics Study 2. Ecological Enhancement Works 3. Initial Observations 4. Way Forwards

Background of the Eco-hydraulics Study Stage 1 Stage 2 1 Select representative green channels 1 Enhancement of RSE and select sites for ecological and water quality field for ecological enhancement site trials. surveys. 2 Detail design of ecological enhancement Develop stream evaluation system to 2 review the ecological value of green works and construction. channels. Water quality and ecological monitoring, Provide ranking of selected channels 3 3 by Rapid Stream Evaluation (RSE) as including pre-enhancement monitoring reference in prioritization of channel (completed) and post enhancement enhancement works. monitoring (on-going). Updating Practice Note 1/2015: Conduct post-enhancement review, 4 4 Guidelines on Environmental and recommendations of operation and Ecological Considerations for River maintenance requirements for upkeeping Channel Design the ecological value. 17/11/2017 Mott MacDonald | Presentation 3

Background of the Eco-hydraulics Study Rapid Stream Evaluation for Green Channels Physical and chemical factors of importance to the biota 1 3 Water quality Embankment 2 indicates the state profile of health of the river channel in the ecological Instream habitat supporting the connectivity to aquatic life adjacent habitats the naturalness and complexity of channel bed substrates for support of aquatic community 17/11/2017 Mott MacDonald | Presentation 4

Background of the Eco-hydraulics Study Rapid Stream Evaluation for Green Channels Biological factors of importance to the biota 1 3 2 Species richness Freshwater/ Species of estuarine fish for native and wetland dependent conservation species concern 4 6 Aquatic Riparian vegetation 5 at water margin & invertebrates embankment Biological indicator Riparian habitat species conditions Habitat diversity and ecological linkage 17/11/2017 Mott MacDonald | Presentation 5

Background of the Eco-hydraulics Study Rapid Stream Evaluation for Green Channels Stage 2 – RSE Criteria (1) Physical and chemical factors (Total 32%) (a) Water quality (8%) (i) pH (2%) (ii) DO (% saturation) (2%) (iii) BOD 5 (2%) (iv) NH 3 -N (2%) (b) Instream habitat – Substrate (6%) (c) Embankment profile (6%) (d) Aquatic habitat quality - Aquatic habitat diversity and longitudinal connectivity (6%) (e) Stream-riparian Ecosystem – Lateral inundation of stream-riparian zone (6%) (2) Biological factors (Total 68%) (a) Species richness (12%) (b) Species of conservation concern (12%) (c) Freshwater/estuarine fish species (12%) (d) Freshwater invertebrates (12%) (e) Riparian habitat conditions (10%) (f) Riparian vegetation at water margin & channel embankment (10%) 17/11/2017 Mott MacDonald | Presentation 6

Background of the Eco-hydraulics Study Rapid Stream Evaluation for Green Channels Categorization of Physical and Chemical Factors for Channels Categories Overall Score 27 – 32 Excellent 22 – 27 Good 16 – 22 Average 8 – 16 Fair 0 – 8 Poor Categorization of Biological Factors for Channels Categories Overall Score 57 – 68 Excellent 47 – 57 Good 34 – 47 Average 17 – 34 Fair 0 – 17 Poor Overall Categorization of Ecological Value and Habitat Quality for Channels Categories Overall Score 85 – 100 Excellent 70 – 85 Good 50 – 70 Average 25 – 50 Fair 0 – 25 Poor 17/11/2017 Mott MacDonald | Presentation 7

Background of the Eco-hydraulics Study Rapid Stream Evaluation for Green Channels – RSE Ranking Fo Tan Nullah and upstream 17/11/2017 Mott MacDonald | Presentation 8

Ecological Enhancement Works

Ecological Enhancement Works Site Trial at Ma Wat River N Site Trial Section A Approx. 80m Site Trial Section B Approx. 250m 17/11/2017 Mott MacDonald | Presentation 10

Ecological Enhancement Works Site Trial at Lower Lam Tsuen River N Site Trial Section Approx. 65m 17/11/2017 Mott MacDonald | Presentation 11

Ecological Enhancement Works Site Trial at Ma Wat River – Baseline Condition (2015) Geography Site Trial Section A River • Fanling • Receive waters Characteristic from Kau Lung Ecology • Trapezoidal Hang, Tai Wo • Grasscrete Stream, Yuen • 96 flora & 54 embankment Leng Stream, faunal spp. • Rip-rap Nam Wa Po • 4 native & channel bed Stream and Ma wetland • Water pools Wat Stream dependent • Meanders • Drain into Ng spp. of Tung River conservation • KLHS & TWS Site Trial Parazacco spilurus concern are EISs and Section B concern species Acrossocheilus beijiangensis 17/11/2017 Mott MacDonald | Presentation 12

Ecological Enhancement Works Site Trial at Ma Wat River – Baseline RSE Score (2015) Criteria Findings (1) Physical and chemical factors of importance to the biota (i) pH 8.5 (ii) DO (% saturation) 106.9 (a) Water quality (iii) BOD 5 (mg/L) 2.9 (iv) NH 3 -N 1.32 Substrate (b) Instream 15% of Mud and Sand; 20% 36% Concrete (Left - Naturalness; Right - habitat Boulder; 29% Pebbles. Heterogeneity) Sloping embankment at both sides with (c) Embankment profile gradient within 35° to 55° (d) Total no. of aquatic habitat 2 Areas need Longitudinal connectivity Water flow blocked by artificial structures improvement (e) Stream-riparian Ecosystem Ranking 2 • In-stream Categories for physical and chemical factors Average habitat (2) Biological factors • Limited aquatic (a) Species richness 15 fauna and poor (b) Species of conservation concern 4 riparian habitat (c) Freshwater/estuarine fish species conditions 11 18% (Left – No. of fish species; Right – Percentage of native species) (d) Freshwater invertebrates 10 2 (Left – No. of aquatic invertebrate species; Right – Number of biological indicators for poor water quality) (e) Riparian habitat conditions 0 (f) Riparian vegetation at water margin & channel embankment 33 60 (Left – No. of wetland plant species; Right: Number of native plant species) Categories for biological factors Fair 13 Overall Categories Average

Opportunity • Enhancement of instream habitat to increase the heterogeneity Project • Enhance the riparian zone Ma Wat River to promote ecological Ecological connectivity Enhancement Site • Provision of microhabitats Trial to facilitate colonisation of aquatic flora and fauna Enhancement works & vegetation planting Solution period • Replacement of concrete 2015 Q4 – 2017 Q1 bed with natural bed materials • Riparian planting • Provision of bio- engineering features • Low-flow channel enhancement Expected outcome • Enhance the physical environment and ecological connectivity for facilitating the colonisation of aquatic flora and fauna 17/11/2017 Mott MacDonald | Presentation 14

Ecological Enhancement Works Site Trial at Ma Wat River – Ecological Enhancement Elements Eco-Friendly Substrates Pools & Riffles Creation Fish Ladder Sinuosity Configuration Palm Roll with Planting Riparian Tree Planting 17/11/2017 Mott MacDonald | Presentation 15

Ecological Enhancement Works Site Trial at Ma Wat River – Hard Engineering Features Current Deflector Installation Palm Fibre Concrete Block Gabion Baskets Reinforced Concrete Grid with Grass Climbers Mesh Planting 17/11/2017 Mott MacDonald | Presentation 16

Ecological Enhancement Works Site Trial at Lower Lam Tsuen River – Baseline Condition (2015) Geography River • Tai Po • Receive waters Characteristic from Upper Lam Ecology • Trapezoidal Tsuen River, • Grasscrete & Pak Ngau Shek • 69 flora & 68 masonry Stream and She faunal spp. embankment Shan River • 7 native & • Concrete • Drain into Tolo wetland channel bed Harbour dependent • Dry weather • Upper LTR & spp. of flow channel PNSS are EISs conservation with concern concern species Little Egret Night Heron Little Egret 17/11/2017 Mott MacDonald | Presentation 17